Category Archives: New Technology

2010 Cadillac SRX Advanced AWD System Delivers High Stability in all Driving Conditions

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VIDEO: 2010 SRX AWD Animation
VIDEO: 2010 SRX AWD Driving
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  • 2010 Cadillac SRX Overview
  • Haldex system offers class-leading performance – up to 100-percent front-to-rear torque transfer
  • Pre-emptive engagement of the rear wheels to optimize traction at take-off
  • Electronic Limited Slip Differential (eLSD) transfers up to 85 percent of torque between rear wheels
  • New rear sub-frame and suspension geometry
  • Available summer 2009

DETROIT – Using cutting-edge technology, the 2010 Cadillac SRX is launching with an advanced all-wheel-drive system (AWD) that delivers best-in-class levels of driver control. The intelligent, active system continuously distributes engine drive torque between the front and rear axles, delivering optimum handling, stability and grip in all driving conditions – from fast corners to slower curves, in dry or wet weather.

“The 2010 SRX will deliver excellent, balanced driving dynamics in all types of weather,” said Bob Reuter, SRX global vehicle chief engineer. “The all-wheel-drive system with electronic limited-slip effectively transfers torque not only from front to rear, but also along the rear axle. This system sets a new benchmark for all all-wheel-drive systems, giving the driver control and confidence on any road surface.”

In honing the integration and performance of the system, Cadillac engineers completed more than 600,000 miles of testing in all weather conditions across some of the most challenging roads in Europe, as well as test tracks in Italy and Spain and the famed Nürburgring circuit in Germany, where Cadillac has developed and validated new vehicle features in recent years. The result is an active, all-wheel-drive system specifically tuned for the SRX. It fully exploits the power of the vehicle’s new, 3.0L direct injected V-6 engine that delivers 265 horsepower (198 kW) at 6,950 rpm and 223 lb.-ft of torque (302 Nm) at 5,100 rpm.

To optimize traction at take-off, the system incorporates an innovative, pre-emptive engagement of the rear wheels. Unlike conventional all-wheel-drive systems, this system eliminates the need to detect front wheel slip before rear drive is activated and sets a new benchmark in all-wheel-drive performance.

Perfect balance

On the road, the AWD system operates seamlessly and is programmed to help the driver keep the car stable, splitting drive torque to counteract oversteer or understeer situations when cornering.

The electronic control unit receives data inputs 200 times every second from more than 20 sensors in the vehicle, including those for the ABS and ESC (Electronic Stability Control) systems. The data processed includes vehicle speed, wheel rotation speeds, lateral acceleration, throttle setting, engine torque, yaw rate and the steering angle. Those inputs are used to continually adjust the torque distribution in response to the driver’s input of steering and throttle, the traction that is available at the individual corners of the vehicle or the intended versus the actual path of the car.

For example, on dry pavement during wide-open throttle, 50 percent of the torque is delivered to the rear, providing acceleration with no wheelspin. On slippery surfaces, torque is delivered to the tires with traction, up to 100 percent in cases where one end of the vehicle is on glare ice. Highway cruising conditions will reduce torque delivery to the rear to 5- to 10-percent, decreasing driveline drag and optimizing fuel economy. In most other driving conditions, the torque varies between 20 percent and 50 percent to the rear axle.

While offering sure-footed handling in low-grip conditions, the SRX AWD system also rewards the enthusiastic driver. The precise balancing of the drive torque reduces ESC throttle and braking interventions, providing smoother and more predictable performance.

Perhaps the most significant aspect of this system, however, is the addition of an active rear limited-slip differential (eLSD). The eLSD can transfer up to 85 percent of maximum rear torque between the rear wheels, to whichever has more grip. Under hard cornering, or when completing a high-speed maneuver, such as a lane change, the application of more or less torque to either wheel helps the rear of the car more closely follow the direction of the front wheels.

The new 2010 SRX’s AWD system is integrated with completely new chassis settings and revised self-leveling rear suspension geometry that delivers a 50-percent increase in camber stiffness. Springs, dampers and the steering system have been specifically tuned for pleasing ride dynamics and good feedback. In addition, the 2010 SRX features tires with a higher speed rating.

How it works

The SRX all-wheel-drive hardware consists of a power take-off unit (PTU) in the front final-drive that transmits engine torque through a prop-shaft to the rear drive module (RDM) that includes a torque transfer device (TTD) and the optional eLSD. Both are wet, multi-plate clutch units from Haldex.

The TTD is activated as soon as the vehicle is placed in gear. RDM clutches are applied and ready to transfer torque before acceleration begins. This pre-emptive function leapfrogs many current technologies that require the detection of wheel slip or driveline rotation before the rear drive is activated. The enhanced functionality provides maximum traction immediately for smooth, strong acceleration from a standstill without the possibility of any drivetrain hesitation. During driving, torque delivery between the axles is varied by a valve in the TTD, which increases or reduces the hydraulic pressure on the wet clutch plates to progressively engage or disengage rear drive. The degree of slip determines the amount of torque transmitted. The eLSD, located alongside the RDM, operates on the same principle as the larger TTD. The electronic control unit functions in concert with the engine, transmission and ABS/ESC control modules.

The 2010 SRX’s AWD system requires the factory installation of a specific rear sub-frame to carry the RDM, as well as the revised rear suspension geometry and new wheel hubs for the drive shafts. The three-piece prop-shaft runs through two bearings with constant velocity joints for smooth running with minimal “wind up.” With the AWD system, the SRX’s wheelbase and rear track dimensions are unaltered from FWD models.

About GM

General Motors Corp. (NYSE: GM), one of the world’s largest automakers, was founded in 1908, and today manufactures cars and trucks in 34 countries. With its global headquarters in Detroit, GM employs 244,500 people in every major region of the world, and sells and services vehicles in some 140 countries. In 2008, GM sold 8.35 million cars and trucks globally under the following brands: Buick, Cadillac, Chevrolet, GMC, GM Daewoo, Holden, Hummer, Opel, Pontiac, Saab, Saturn, Vauxhall and Wuling. GM’s largest national market is the United States, followed by China, Brazil, the United Kingdom, Canada, Russia and Germany. GM’s OnStar subsidiary is the industry leader in vehicle safety, security and information services. More information on GM can be found at www.gm.com.

General Motors’ Newest Engines Help Save Fuel And Money

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  • New technologies and vehicle enhancements will enable GM’s 2009 domestic car and light truck lineups to save 700 million gallons of fuel over vehicle life as compared to the 2008 GM fleet
  • Chevy Equinox four-cylinder model to offer class-leading highway fuel economy

PONTIAC, Mich. – Owners of the 2010 Chevrolet Equinox crossover will hit the streets next summer in a vehicle equipped with a highly efficient, all-new engine that will help save both fuel and money.

The 2010 Equinox will be offered with a choice of two new direct injected (DI) engines that use less fuel yet make more power – a 2.4L four-cylinder and a 3.0L V-6. The 2.4L engine delivers an estimated 30 mpg in highway driving (EPA certification pending), placing the Equinox at the top of its segment in highway mileage. Consumers who drive the 2.4L-equipped Equinox 15,000 miles per year will save 134 gallons of fuel or about $270 to $400 annually (assuming gas prices of $2 or $3 per gallon as compared to 2009MY Equinox).

The Equinox will join a growing roster of direct injected vehicles from GM, including the all-new 2010 Cadillac SRX crossover and 2010 Buick LaCrosse sedan, which, along with the Equinox, debut in January at the North American International Auto Show in Detroit. In fact, for the 2010 model year, GM will offer more DI models in North America than any other manufacturer.

“We first introduced direct injection in North America in the 2007 Saturn Sky Red Line and the Pontiac Solstice GXP,” said Tom Stephens, executive vice president, GM Global Powertrain and Global Quality. “We’ve been rolling out the technology across our portfolio as quickly as we can so that our customers will have additional fuel savings options. Direct injection is a state-of-the art engineering solution because it enables improved fuel economy and lower emissions without sacrificing power.”

In the 2009 model year, GM offers six engines in 18 models globally with direct injection. By 2010, GM will have eight direct injected engines in 38 vehicle models, covering 10 percent of its global volume. In North America alone, GM will offer 18 models with direct injection.

GM’s fuel-saving lineup

GM’s direct injection push is part of a larger effort to implement multiple fuel-saving technologies across its 2009 portfolio. The all-new 2009 Chevy Traverse crossover, for example, enjoys best-in-class highway fuel economy (24 mpg for FWD models) of any eight-passenger SUV, thanks in part to its 3.6L direct injected V-6 engine with variable valve timing. In 2009, GM expects to sell 500,000 vehicles with gasoline direct injection.

Here are additional fuel-saving facts about GM vehicles:

  • Twenty models in GM’s 2009 lineup deliver EPA-rated highway fuel economy of 30 mpg or more – more than any other automaker. GM’s non-hybrid models rank first in highway fuel economy in both the midsize sedan and subcompact segments. (Chevrolet Malibu, Saturn Aura with 33 highway mpg; and Chevrolet Colbalt XFE and Pontiac G5 XFE at 37 highway mpg.)
  • GM’s 2009 domestic car and light truck lineups will use 700 million fewer gallons of fuel than the 2008 lineup, during the life of the vehicles, saving $1.4 to $2.1 billion in fuel costs, assuming gas prices of $2 to $3 per gallon. It’s estimated that GM’s 2010 lineup will add another 1.1 billion gallons of fuel savings and $2.2 to $3.3 billion, relative to the 2008 lineup.

GM’s advanced engine technologies are already saving fuel today in vehicles on the road or expected to be sold in 2009. They include:

  • More than 3.7 million vehicles with variable valve timing (VVT)
  • 700,000 vehicles with direct injection
  • 600,000 vehicles with Active Fuel Management cylinder deactivation technology, which automatically lets the engine run on half of its cylinders when full power is not needed
  • 200,000 vehicles with turbocharged gas engines
  • 42,000 vehicles with both direct injection and turbocharging
  • More than 2 million vehicles with fuel-saving six-speed transmissions

2.4L DI details

The new 2.4L DI engine delivers an estimated 180 horsepower (134 kW) @ 6700 rpm and 172 lb.-ft. of torque (232 Nm) @4900 rpm. It uses technology based on GM’s other four-cylinder direct injection applications, but with unique features designed for its specific application. This includes an 11.4:1 compression ratio that helps build power, slightly dished pistons that increase combustion efficiency and injectors with an application-specific flow rate.

GM benchmarked the best fuel system and noise attenuation products to provide customers with quiet operation.

3.0L DI details

The new 3.0L DI engine is a variant of GM’s family of high-feature DOHC V-6 engines that also includes GM’s 3.6L DI engine in the Cadillac CTS – an engine named to Ward’s AutoWorld’s 2009 “Ten Best Engines” list for North America, for the second consecutive year.

The 3.0L is rated at an estimated 255 horsepower (187 kW) and 214 lb.-ft. of torque (290 Nm), for an impressive power-to-displacement ratio of 85 hp per liter. (Output will vary by model.) The 3.0L DI features an isolated fuel injector system that reduces the direct injection high-pressure fuel system pulses for quieter operation. Rubber isolators are used with the fuel rail to eliminate metal-to-metal contact that would otherwise transmit noise and vibration from the high-pressure fuel system.

Along with direct injection technology, both the 3.0L DI and 2.4L DI engines use variable valve timing to optimize power and fuel efficiency across the rpm band, as well as reduce emissions.


How DI Works Animation

How DI works

In a conventionally port fuel injected engine, air and fuel are mixed before they enter the combustion chamber. With GM’s DI engines, fuel is sprayed directly into the cylinder where it is mixed with air. As the piston approaches top-dead center, the mixture is ignited by the spark plug; and when the fuel vaporizes in the cylinder, the air and fuel mixture is cooled. This enables the use of a higher compression ratio in the combustion chamber, which improves the engine’s power and efficiency.

On cold starts, direct injection can be controlled to create a richer air/fuel mixture around the spark plug, making it easier to ignite in a cold engine. This results in a smoother operation of the engine andlower emissions during the cold start and warm-up, when most harmful tailpipe emissions are typically created. GM’s direct injected engines reduce cold-start vehicle emissions by 25 percent.

Because the fuel is injected directly into the combustion chamber, direct injection uses higher fuel pressure than conventional fuel injected engines. This is enabled by a special high pressure pump driven by one of the engine’s camshafts.

Direct Injection Awarded

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Automobile Magazine has named Direct Injection as a “2009 Technology of the Year”.  I would certainly agree on it for 2008; may be a bit early for 2009.

Direct Injection is used on the 3.6L DI V6 and the RWD Northstar 4.6L V8 in Cadillacs.  Normal fuel injection sprays fuel into the intake tract of the engine.  The incoming air then mixes with the fuel to form a fuel/air vapor that travels into the cylinder.  Direct Injection on the other hand uses high pressure fuel injectors to spray fuel directly into the cylinder itself.  This allows the system to more closely control the combustion process, resulting in more horsepower and a slightly lower specific consumption, meaning greater economy.